This invention relates to microwave devices, and more particularly to structures for interconnecting between coaxial transmission line and suspended air stripline.
A typical technique for providing a vertical RF interconnect with a coaxial line uses hard pins. Hard pin interconnects do not allow for much variation in machine tolerance. Because hard pins rely on solder or epoxies to maintain electrical continuity, visual installation is required, resulting in more variability and less S-Parameter uniformity.
Another interconnect technique is a pin/socket type, blind mate interconnect. Pin/socket interconnects usually employ sockets which are much larger than the pin they are capturing. This size mismatch may induce reflected RF power in some packaging arrangements. For interconnects to airline, stripline or similar transmission lines, a pin would have to be soldered onto the surface of the circuit, causing more assembly and repair time.
An RF interconnect is described between an airline circuit including a dielectric substrate having a conductor trace formed on a first substrate surface and an RF circuit separated from the airline circuit by a separation distance. The RF interconnect includes a compressible conductor structure having an uncompressed length exceeding the separation distance, and a dielectric sleeve structure surrounding at least a portion of the uncompressed length of the compressible conductor structure. The RF interconnect structure is disposed between the substrate and the RF circuit such that the compressible conductor is placed under compression between the substrate and the RF circuit.
In one exemplary embodiment, the RF circuit is a coaxial transmission line including a coaxial center conductor, the center conductor extending transverse to the airline substrate. The compressible conductor is under compression between the coaxial center conductor and the substrate. In another embodiment, the RF circuit is a grounded coplanar waveguide (GCPW) circuit including a GCPW dielectric substrate with a first surface having a conductor center trace and a ground conductor pattern formed thereon, the compressible conductor under compression between the GCPW substrate and the airline substrate.
The compressible conductor can take many forms, including a bundle of densely packed thin wire, a bellows or a spring-loaded retractable probe structure. The compressible center conductor maintains a good physical contact without the use of solder or conductive epoxies.